The present invention relates to alkoxy-functional RTV compositions, and more particularly, the present invention relates to alkoxy-functional, one-component, RTV compositions having novel scavengers which scavengers can also be utilized as cross-linking agents in some cases. (RTV in this patent application refers to room temperature vulcanizable).
One-component and two-component, alkoxy-functional RTV compositions are well known. See, for instance, the disclosures of Beers, U.S. Pat. No. 4,100,129, Nitzsche et al., U.S. Pat. No. 3,127,363, and Nitzsche et al., U.S. Pat. No. 3,065,194. Recently, there has been discovered or invented, novel one-component, alkoxy-functional, RTV compositions which are shelf stable. It is postulated that in previous alkoxy-functional, one-component, RTV compositions, that the composition after being prepared and upon standing, and as a result of having excess hydroxy groups in the polymer mixtures, the polymer mixture would degrade such that it would not cure at a sufficient rate after having been stored for any substantial period of time such as a month or more. Even if such a composition would cure after prolonged storage, still the cured composition did not achieve its maximum or optimum physical properties. It should be noted that even commerical, one-component, alkoxy-functional, RTV compositions, such as that of Beers, U.S. Pat. No. 4,100,129 mentioned above, suffered to some extent from this problem.
The hypothesis for the reasons for the problem as well as the solutions to the problem, i.e., shelf-stable, one-component, alkoxy-functional, RTV system, is to be found more fully set forth in White et al., U.S. Pat. No. 4,395,526, which is hereby incorporated by reference. A related case is Halgren, U.S. Pat. No. 4,377,706. Basically, these patents, and particularly, White et al., disclose the use of scavengers and integrated scavengers and cross-linkers having certain types of functionality to be utilized to absorb or react with all or most of the hydroxy groups in the polymer mixture such that the polymer mixture will remain shelf-stable.
Other related applications that have been filed since the filing of the White et al. case are for instance, Chung, Ser. No. 338,518, filed Jan. 11, 1982, now U.S. Pat. No. 4,424,157. The Chung case relates to the use of cyclic amides or novel cyclic amide compounds as scavengers and integrated cross-linking agents for the RTV systems of White et al.
Since that time, there have also been filed Beers. Ser. No. 349,537, and now abandoned, Lucas et al., Ser. No. 349,538, now U.S. Pat. No. 4,483,973, and Dziark, Ser. No. 349,695, now U.S. Pat. No. 4,417,042, all filed on Feb. 17, 1982. The Beers application relates to the use of various ingredients in the composition to render the composition low-modulus with good self-bonding properties. The patent application of Lucas et al., relates to the use of certain novel, self-bonding additives for the RTV composition of White et al. Finally, the Dziark patent, U.S. Pat. No. 4,417,042, relates to the use of certain silazane compounds as scavengers for the basic RTV compositions disclosed in White et al. However, it should be noted that the silazane compounds of Dziark, U.S. Pat. No. 4,417,042, are solely scavengers. That is, they are utilized after the alkoxy-terminated, diorganopolysiloxane polymer is first formed. After it is formed, then the silazane scavengers of Dziark, are added. These silazane compounds of Dziark, most of which are well known, react with the hydroxy groups in the polymer mixture and tie them up such that they cannot react or further cross-link to degrade the basic polymer that is needed in the system. Further, in the compositions of Dziark, as disclosed in one aspect in White et al., the alkoxy-terminated diorganopolysiloxane polymer has to be formed first, by reacting a silanol-terminated diorganopolysiloxane polymer with an alkyl trialkoxysilane in the presence of an amine. Then once the multialkoxy-terminated diorganopolysiloxane polymer is formed, the scavenger can be added to the system along with the other ingredients to react with all the hydroxy groups in the RTV system.
The silazane scavengers of Dziark suffer from the fact that they cannot be utilized as cross-linkers; that is, they can be used only as scavengers. As noted in White et al it is desirable also in many cases to have integrated cross-linker scavengers, which materials can act both as scavengers and as cross-linking agents, for the White et al. RTV systems.
Accordingly, it was highly desirable to find silazane cross-linker scavenger compounds which could be utilized in the White et al. systems. Specifically, silazane scavengers and silazane integrated cross-linkers as scavengers are desirable since they are inexpensive to make, they give a by-product of ammonia when they react with the hydroxy groups which ammonia is innocuous. Another advantage of such silazane scavengers and integrated cross-linkers is that only a small amount of such compounds is needed to effect the necessary tying up of the hydroxy groups in the polymer system. This results from the high functionality of the silazine compounds and the nitrogen agents that tie up or bond with the hydroxy groups in the polymer systems.
Accordingly, it is one object of the present invention to provide for novel silazane scavengers for alkoxy-functional, one-component, RTV systems.
It is another object of the present invention to provide for novel integrated cross-linkers, scavengers for alkoxy-functional, one-component, RTV systems.
It is still an additional object to provide for alkoxy-functional silazane which can be utilized either as a scavenger or as an integrated scavenger, cross-linking agent for alkoxy-functional, one-component, RTV systems.
It is still an additional object of the present invention to provide a method for producing shelf-stable, alkoxy-functional, one-component, RTV systems by including in the composition an alkoxy-functional silazane which can act both as a scavenger and, if desired, as an integrated cross-linking agent and scavenger.
It is yet still a further object of the present invention to provide a method for producing a shelf-stable, alkoxy-functional, one-component, RTV system by incorporating in the composition, an alkoxy-functional silazane which can act either as a scavenger or as an integrated cross-linker scavenger for the systems.
These and other objects of the present invention are accomplished by the disclosures set forth herein below.